This invention related to the production of epoxy cellular solid products by reacting an epoxy compound with an organic polyamine compound to produce an epoxy prepolymer. The epoxy prepolymer expands when heated to produce an epoxy cellular solid, without the addition of a blowing agent. Various organic and inorganic compounds and polymers may be added to the prepolymer to give the desired physical properties.
The epoxy cellular solids may be produced as a rigid, semi-rigid, flexible or elastic cellular solid. The liquid epoxy prepolymer expands 3 to 12 times its original volume to produce the cellular solid. The epoxy cellular solids have a number of diverse applications. They may be molded into useful cellular solid products by pouring the prepolymer into a mold and heating it at 80.degree. C. to 100.degree..degree. C. The cellular solid may be used for insulation, floatation, strengthening material, packaging material and for its acoustic properties. The epoxy cellular solid may be produced as a soft cellular solid and is biodegradable.
Foamed epoxy resins have been produced by the use of a blowing agent as illustrated in U.S. Pat. Nos. 3,420,794; 2,831,820; 2,739,134; 2,987,482; 3,129,191; 3,154,504; 3,198,756; 3,282,863; 3,373,121; 4,043,950; and 4,143,009, but none of these U.S. Patents produce foamed epoxy resins without the use of blowing agents (foaming agents). The process of this invention is different from the listed U.S. Patents by the fact that no blowing agent needs to be added in order to produce the foamed cured epoxy resin. In the listed U.S. Patents such as U.S. Pat. No. 3,420,794, a special activator and a foaming agent (blowing agent) such as the chlorofluoralkanes known as "Freons", is necessary in order to produce the foam. In that U.S. Patent, a foaming agent (blowing agent) is mixed with the epoxy resin and curing agent, then the mixture is heated to expand the blowing agent, thereby producing the foamed cured epoxy resin. In the present invention, the epoxy resin is expanded to produce a foam by the release of a gas from the epoxy resin molecule when it is heated to above 80.degree. C. The exact composition of the gas produced is not known, but appears to be a combination of carbon dioxide, nitrogen and oxygen.